<!doctype html>
<html lang="en">
 <head>
  <meta charset="UTF-8">
  <meta name="Generator" content="EditPlus®">
  <meta name="Author" content="">
  <meta name="Keywords" content="">
  <meta name="Description" content="">
  <title>Document</title>
 </head>
 <body>
    <button id="but" onclick="show()">点击切换图片<button> <br>
	<img src="img/img_14.jpg" id = "img" width="100px" height="100px">
 </body>
 <script>
    var i = 1;
    function show(){
	  var img = document.getElementById("img");
      if(i == 1){
	     img.src="img/img_15.jpg";
	  }else if(i == 2){
	  
	     img.src="img/img_16.png";
	  }
	  else{
	     img.src="img/img_14.jpg";
		 i = 0;
	  }
	  i ++;
	}
 </script>
</html>
